One of my new ones is doing that. He goes after them but they keep popping out of his mouth. He's kind of small so I think the pellets are a bit big for him. I'm feeding him Nutrafin max that I got from somewhere. It's a flake food and when my fish gets a little bigger, I'll feed him the pellets. The pellets are Hikari Betta bio gold. You could try crushing up the pellets and see if he does any better with that.